Strong’s Exhaustive Concordance of the Bible was a fine reference work in the age of print, it allowed people to find where particular words were used in the Bible. Through two series of numbers (one for the Greek words of the NT and one for the Hebrew words of the OT) attached to the words in an English translation, people who do not know the languages of the Bible can get behind the translation.
These numbers have been used in many of the free, and paid for, Bibles on computers and phones. They are also available in online Bibles. The videos below show how to use them in Blueletter Bible and in STEP Bible (Scripture Tools for Every Person is a new project I have been involved with, from tyndale House in Cambridge, that is easier, neater and offers an increasing and wonderful range of resources!)